The present invention relates to a toroidal continuously variable transmission (toroidal CVT) for a vehicle, and more particularly to a structural arrangement of a toroidal CVT.
Japanese Patent Provisional Publication NO. 6-34009 discloses a toroidal CVT of a half toroidal type in which first and second wires are wound in the shape of 8-figure to two pairs of power-roller supporting members respectively and a third wire is wound around the four power-roller supporting members while being fixed to two diagonally arranged power-roller supporting members.
However, such a wire, particularly a third wire, in a toroidal CVT is simply wound to four power-roller supporting members (trunnions), and therefore the toroidal CVT employing such a wire arrangement has the following problems.
First, it is necessary to provide a cylindrical portion at an upper portion of each power-roller supporting member for the wire. This provision of the cylindrical portion elongates the power roller supporting member and therefore the size of the toroidal CVT becomes large.
Since it is necessary to set the length of the third wire with a sufficient margin, there is a tendency that a play of the third wire is caused between the diagonally arranged power-roller supporting members. This degrades a synchronized responsibility or an accuracy of the synchronicity during the synchronization of a gyration angle (tilting rotation angle) of the four power rollers.
It is therefore an object of the present invention to provide an improved toroidal CVT which is advantageous in the fixing strength of a third wire while suppressing a play of a third wire between the diagonally arranged power roller supporting members.
A toroidal continuously variable transmission (CVT) according to the present invention comprises first and second input discs coaxially connected to an input shaft; first and second output discs coaxially disposed between the first and second input discs; pressure means for applying a pressing force along an axial direction of the toroidal CVT to the pair of the input discs; first and second power rollers disposed between the first input disc and the first output disc; third and fourth power rollers disposed between the second input disc and the second output disc; first, second, third and fourth power-roller supporting members supporting the first and second pairs of power rollers, respectively; a first wire wound in a shape of 8-figure to the first and second power-roller supporting members; a second wire wound in a shape of 8-figure to the third and fourth power-roller supporting members; a third wire wound around the first, second, third and fourth power roller supporting members and fixed to the first and third power-roller supporting members diagonally arranged; and guide walls disposed between the first and second power-roller supporting members and between the third and fourth power-roller supporting members, respectively, the guide walls bending the third wire extended between the first and second power-roller supporting members and between the third and fourth power-roller supporting members toward the output discs.